Designed for hard, strong or brittle nails, Jessica Professional Emery Boards for Hard Nails contains two professional emery boards designed specifically for the needs of overly hard nails. Natural nails are composed of delicate layers that seal together for strength, so using the wrong nail file can separate and damage these layers resulting in flaking and peeling nails. Jessica Professional Emery Boards for Hard Nails have been created to address hardened nails, helping shape them for optimum health. Directions of use: Gently file in one direction. Do not \'saw\' back and forth. Avoid filing into the sides of your nail as they provide strength and support. The shape of the free edge of the nail should reflect the shape of your cuticle. Filing your nails as recommended, using the correct emery board will promote healthy growth. Toe nails should be filed straight across to avoid ingrowing nails.